not stacking

I've had players say they can't stack cctv's, for example. when they loot the aforementioned cctv from a container, sometimes it shows a loading symbol, like when a skin hasn't loaded in for the item. They aren't able to stack these with any other cctv's. Many items have the loading symbol even though I don't have any custom items in the plugin. I haven't even really added anything, only taken out the junk. Why is this happening and how do I fix it?